Implantable medical device including a conductive fixation element

ABSTRACT

A system comprises an implantable medical device and an actively deployable clip attached to the implantable medical device to restrict movement of the implantable medical device once the clip is deployed within a body of a patient. The clip includes an electrically conductive portion. The implantable medical device may be implanted proximate to any suitable tissue site within the patient, and in one embodiment, the implantable medical device is implanted proximate to an occipital nerve or a trigeminal nerve of the patient.

TECHNICAL FIELD

The invention relates to implantable medical devices and, moreparticularly, to techniques for fixation of implantable medical deviceswithin a body of a patient.

BACKGROUND

Electrical stimulation systems may be used to deliver electricalstimulation therapy to patients to treat a variety of symptoms orconditions such as chronic pain, tremor, Parkinson's disease, multiplesclerosis, spinal cord injury, cerebral palsy, amyotrophic lateralsclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders,gastroparesis, muscle stimulation (e.g., functional electricalstimulation (FES) of muscles) or obesity. An electrical stimulationsystem typically includes one or more stimulation leads coupled to anelectrical stimulator.

The neurostimulation lead may be percutaneously or surgically implantedin a patient on a temporary or permanent basis such that at least onestimulation electrode is positioned proximate to a target stimulationsite. The target stimulation site may be, for example, a nerve or othertissue site, such as an occipital nerve, spinal cord, pelvic nerve,pudendal nerve, stomach, bladder, or within a brain or other organ of apatient, or within a muscle or muscle group of a patient.

Electrical stimulation of a peripheral nerve, such as stimulation of anoccipital nerve or a trigeminal nerve, may be used to induceparesthesia. Occipital nerves, such as a lesser occipital nerve, greateroccipital nerve or third occipital nerve, exit the spinal cord at thecervical region, extend upward and toward the sides of the head, andpass through muscle and fascia to the scalp. Pain caused by an occipitalnerve, e.g. occipital neuralgia, may be mitigated by deliveringstimulation therapy to the occipital region via an implanted stimulationlead.

In many electrical stimulation applications, it is desirable for astimulation lead to resist migration following implantation. Forexample, it may be desirable for the electrodes disposed at a distal endof the implantable medical lead to remain proximate to a targetstimulation site in order to provide adequate and reliable stimulationof the target stimulation site. In some applications, it may also bedesirable for the electrodes to remain substantially fixed in order tomaintain a minimum distance between the electrode and a nerve in orderto help prevent inflammation to the nerve and in some cases, unintendednerve damage. Securing the stimulation lead at the target stimulationsite may minimize lead migration.

SUMMARY

In general, the invention is directed to techniques for fixation of animplantable medical device, such as an electrical stimulator, lead orcatheter, via an actively deployable fixation clip that is coupled tothe implantable medical device. The fixation clip is configured tochange from a first shape in an undeployed state to a second shape in adeployed state. In the deployed state, the fixation clip is configuredto engage with surrounding tissue to substantially fix a position of theimplantable medical device proximate to a target tissue site within apatient. In one embodiment, the target tissue site is an occipitalnerve, a trigeminal nerve, and/or branches of the occipital andtrigeminal nerves of a patient.

In accordance with one aspect of the invention, the fixation clip isattached directly or indirectly to a lead that is configured to deliverelectrical stimulation therapy from an electrical stimulation generatorto a target stimulation site within a patient. In one embodiment, thefixation clip includes an electrically conductive portion, such as aportion comprising a shape memory metal, which may be an electrode ofthe lead. The electrically conductive fixation clip may substantiallyfix a position of the lead as well as deliver electrical stimulation tothe target stimulation site within a patient.

In one embodiment, the invention is directed to system comprising animplantable medical device and a fixation element coupled to theimplantable medical device. The fixation element comprises anelectrically conductive portion configured to at least one of deliverelectrical stimulation to a target tissue site within a patient or sensea physiological parameter from the target tissue site. The fixationelement is actively deployable from a first shape to a second shape toresist substantial movement of the implantable medical device from thetarget tissue site.

In another embodiment, the invention is directed to a medical leadcomprising a lead body, an electrical conductor disposed within the leadbody, and a fixation element comprising an electrically conductiveportion electrically coupled to the electrical conductor. The fixationelement is actively deployable from a first shape to a second shape toresist substantial movement of the lead body from a target therapydelivery site in a patient.

In yet another embodiment, the invention is directed to a methodcomprising implanting an implantable medical device in a body of apatient, and actively deploying a fixation element coupled to theimplantable medical device. The fixation element comprises anelectrically conductive portion configured to at least one of deliverelectrical stimulation to a target tissue site within the body of thepatient or sense a physiological parameter from the target tissue site.The fixation element is actively deployable from a first shape to asecond shape to resist substantial movement of the implantable medicaldevice from the target tissue site.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a therapy system including a lead fixedproximate to an occipital nerve of a patient via an actively deployablefixation clip.

FIG. 2 illustrates the lead of FIG. 1, which is aligned to be introducedinto an introducer needle that is positioned proximate to an occipitalnerve of the patient.

FIG. 3 is a block diagram illustrating various components of anelectrical stimulator and the implantable medical lead of FIG. 1.

FIG. 4A is a schematic perspective view of the lead of FIG. 1, where afixation clip of the lead is in an undeployed state.

FIG. 4B is a schematic perspective view of the lead of FIG. 1, where theclip is in a deployed state.

FIG. 5A is a schematic diagram illustrating the lead of FIG. 1 implantedwithin a patient proximate to an occipital nerve, where the clip hasbeen deployed into tissue adjacent to the occipital nerve.

FIG. 5B is a schematic diagram illustrating the lead of FIG. 1 implantedwithin a patient proximate to an occipital nerve, where the clip hasbeen deployed such that the clip wraps around the occipital nerve.

FIGS. 6A-6C are schematic perspective views of a lead including anotherembodiment of a clip retainer mechanism.

FIG. 7 illustrates a schematic perspective view of another embodiment ofa lead, which includes actively deployable clips disposed along alongitudinal outer surface of a lead body.

FIG. 8 is a schematic diagram illustrating the lead of FIG. 7 implantedwith a patient proximate to an occipital nerve.

FIG. 9 is a schematic perspective view of another embodiment of a lead,which includes actively deployable clips disposed along the same side ofa longitudinal outer surface of a lead body.

FIG. 10 is a schematic perspective view of another embodiment of a lead,which includes an actively deployable clip extending between electrodesof the lead.

FIGS. 11 and 12 are schematic plan views of paddle leads includingactively deployable fixation clips for fixing a position of the paddlelead proximate to a target tissue site in a patient.

FIG. 13 is a block diagram of a process of implanting a lead includingan actively deployable fixation clip within a body of a patient.

DETAILED DESCRIPTION

The present invention relates to actively deployable clips for fixing animplantable medical device proximate to a target tissue site within apatient. The implantable medical device is configured to deliver atherapy to the target tissue site. Various embodiments of theimplantable medical device may be applicable to different therapeuticapplications. In some embodiments, the implantable medical device isconfigured to couple to a therapy delivery source, such as an electricalstimulation generator or a fluid delivery device. For example, theimplantable medical device may be a stimulation lead or a lead extensionthat is used to deliver electrical stimulation to a target stimulationsite and/or sense parameters (e.g., blood pressure, temperature orelectrical activity) proximate to a target site within a patient. Inanother embodiment, the implantable medical device may be a catheterthat is placed to deliver a fluid, such as pharmaceutical agents,insulin, pain relieving agents, gene therapy agents or the like from afluid delivery device (e.g., a fluid reservoir and/or pump) to thetarget tissue site within the patient. In yet another embodiment, theimplantable medical device may be a microstimulator that may beimplanted within tissue of a patient to deliver stimulation to thetissue. Thus, in some embodiments, “therapy” may include stimulationtherapy, sensing or monitoring of one or more physiological parameters,fluid delivery, and the like. “Target tissue site” refers generally tothe target site for implantation of an elongated member, regardless ofthe type of therapy.

The invention is applicable to any configuration or type of implantablemedical device that is used to deliver therapy to a nerve, organ,muscle, muscle group, or other tissue within a patient. For purposes ofillustration, however, the disclosure will refer to a neurostimulationlead.

In one embodiment, the target tissue site is proximate to an occipitalnerve site or trigeminal nerve site within a patient, such as tissueadjacent to the occipital nerve or the trigeminal nerve or a nervebranching from the occipital and/or trigeminal nerve. Thus, reference toan “occipital nerve” or a “trigeminal nerve” throughout the disclosurealso includes branches of the occipital and trigeminal nerves,respectively. In addition, the therapy may be delivered to both anoccipital nerve and trigeminal nerve within the patient.

FIG. 1 is a schematic view of a head and torso of patient 10, in whichof a lesser occipital nerve 12, greater occipital nerve 14, and thirdoccipital nerve 16 of patient 10 are shown. Occipital nerves 12, 14, and16 generally extend upward from a spinal cord of patient 10 to the backand sides of the head. Also shown in FIG. 1 is therapy system 20, whichincludes electrical stimulator 22 and implantable medical lead 24, whichextends between proximal end 24A and distal end 24B, and includesstimulation electrodes 26 proximate to distal end 24B. Electricalstimulator 22 provides electrical stimulation via one or more electrodes26 of lead 24 to target stimulation site 28, which in the embodimentshown in FIG. 1, may be adjacent to at least one of lesser occipitalnerve 12, greater occipital nerve 14 or third occipital nerve 16 ofpatient 10. In the embodiment shown in FIG. 1, electrodes 26 of lead 24are implanted proximate to third occipital nerve 16. In alternateembodiments, lead 24 may be positioned proximate to one or more otherperipheral nerves proximate to occipital nerves 12, 14, 16 of patient10, such as nerves branching from occipital nerves 12, 14 or 16.

Stimulation of target stimulation site 28 (i.e., in regions of patient10 proximate to occipital nerves 12, 14, and/or 16) may help alleviatepain associated with, for example, chronic migraines, cervicogenicheadaches, occipital neuralgia or trigeminal neuralgia.

In the embodiment shown in FIG. 1, electrical stimulator 22 is aneurostimulator that is either implantable or external. FIG. 1illustrates neurostimulator 22 implanted within a chest cavity ofpatient 10. In other embodiments, neurostimulator 22 may be implanted inany suitable location of patient 10. For example, neurostimulator 22 maybe subcutaneously implanted in the body of patient 10 within a lowerback, lower abdomen, proximate to the trapezius muscle 25 of patient 10,or buttocks of patient 10. Neurostimulator 22 provides a programmablestimulation signal (e.g., in the form of electrical pulses orsubstantially continuous-time signals) that is delivered to targetstimulation site 28 by implantable medical lead 24, and moreparticularly, via one or more stimulation electrodes 26 carried by lead24. Neurostimulator 22 may also be referred to as a pulse generator. Insome embodiments, lead 24 may also carry one or more sense electrodes topermit neurostimulator 22 to sense electrical signals from targetstimulation site 28.

In some embodiments, neurostimulator 22 may be coupled to two or moreleads, e.g., for bilateral or multi-lateral stimulation. For example,therapy system 20 may include two leads, where one lead is positionedproximate to a branch of occipital nerve 12, 14, or 16 on each side ofthe head of patient 10 (i.e., on each side of the midline) to achievebilateral stimulation. Midline 11 is a schematic representation of theline that divides patient 10 into approximately equal and symmetricalleft and right halves. Delivering therapy to two target tissue sites maybe used to deliver therapy to two nerve branches that branch from thesame nerve. Nerves may branch into left and right branches that extendto opposite sides of midline 11, and therapy is delivered to two nervebranches on opposite sides of midline 11. Stimulation of two nervebranches on opposite sides of midline 11 may be referred to as bilateralstimulation. However, bilateral stimulation may also refer tostimulation of any two regions of patient 10 either sequentially orsimultaneously. Delivering therapy after nerves branch, e.g., closer tothe nerve endings, may allow more targeted therapy delivery with fewerside effects.

Bilateral stimulation may also be achieved with a single lead 24, whereelectrodes 26 of lead 24 are positioned to span both regions ofstimulation. For example, bilateral stimulation of an occipital nervemay be achieved by utilizing a single lead 24 that is placed such thatelectrodes 26 span both sides of the midline 11 of patient 10 andproximate to the branches of the occipital nerve to be stimulated.

Proximal end 24A of lead 24 may be both electrically and mechanicallycoupled to connector 23 of neurostimulator 22 either directly orindirectly (e.g., via a lead extension). In particular, conductorsdisposed within a lead body of lead 24 electrically connect stimulationelectrodes 26 (and sense electrodes, if present) located adjacent todistal end 24B of lead 24 to neurostimulator 22. Proximal end 24A oflead 24 may include electrical contacts that correspond to each of theconductors that are electrically connected to electrodes 26, where theelectrical contacts electrically couple electrodes 26 to neurostimulator22.

Lead 24 further includes an actively deployable clip fixation element 30attached to lead 24 to help substantially fix lead 24 proximate totarget stimulation site 28. In FIG. 1, clip 30 is in a deployed state.Although one clip 30 is shown in FIG. 1 attached to distal end 24B oflead 24 and near electrodes 26, in other embodiments, lead 24 mayinclude more than one or more clips arranged in any suitable fashionwith respect to lead 24. Clip 30 may be formed from elastic, shapememory materials, or any other material that is capable of changingshape upon release of a retainer mechanism. In some embodiments, atleast a portion of clip 30 may be electrically conductive, therebyenabling clip 30 to act as an electrode of lead 24. For example, clip 30may be a sensing electrode or a stimulation electrode of lead 24.

As described in further detail below, actively deployable clip 30 may bedeployed by releasing clip 30 from a retainer mechanism. For example, aretainer wrap, band or binder may be cut, broken or withdrawn to releaseclip 30. Deployment of actively deployable clip 30 by releasing it fromretainer mechanism permits clip 30 to initiate a shape change due togeneral elasticity or shape memory properties. For example, clip 30 maychange from a substantially straight or slightly curved shape, prior todeployment, to a moderately or highly curvilinear or spiral shape,following deployment, as shown in FIG. 1. The post-deployment shape ofclip 30 may be a regular or irregular shape, provided that clip 30assumes a shape that interacts and engages with body tissue to resistmovement of lead 24. In particular, it is desirable for electrodes 26 toremain within an operative distance with respect to target stimulationsite 28 following implantation of lead 24 within patient 10.

In other embodiments, target tissue site 28 (which may be a targettherapy delivery site) may be a location proximate any suitable nerve,organ, muscle or muscle group within a patient, which may be selectedbased on, for example, a therapy program selected for a particularpatient. For example, therapy system 20 may be used to deliverelectrical stimulation therapy to a sacral nerve, a pudendal nerve, aperineal nerve, a trigeminal nerve or other areas of the nervous system,in which cases, lead 24 would be implanted and substantially fixedproximate to the respective nerve. As further examples, lead 24 may bepositioned for temporary or chronic spinal cord stimulation for thetreatment of pain, for peripheral neuropathy or post-operative painmitigation, ilioinguinal nerve stimulation, intercostal nervestimulation, gastric stimulation for the treatment of gastric mobilitydisorders and obesity, muscle stimulation (e.g., functional electricalstimulation (FES) of muscles), for mitigation of other peripheral andlocalized pain (e.g., leg pain or back pain), or for deep brainstimulation to treat movement disorders and other neurologicaldisorders. Accordingly, although patient 10 and target stimulation site28 of FIG. 1 are referenced throughout the remainder of the disclosurefor purposes of illustration, a neurostimulation lead 24 in accordancewith the invention may be adapted for use in a variety of electricalstimulation applications in addition to occipital nerve stimulation.

Therapy system 20 may also include clinician programmer 36 and patientprogrammer 38. Clinician programmer 36 may be a handheld computingdevice that permits a clinician to program electrical stimulationtherapy for patient 10, e.g., using input keys and a display. Forexample, using clinician programmer 36, the clinician may specifyelectrical stimulation parameters for use in delivery ofneurostimulation therapy. Clinician programmer 36 supports telemetry(e.g., radio frequency (RF) telemetry) with neurostimulator 22 todownload neurostimulation parameters and, optionally, upload operationalor physiological data stored by neurostimulator 22. In this manner, theclinician may periodically interrogate neurostimulator 22 to evaluateefficacy and, if necessary, modify the stimulation parameters.

Like clinician programmer 36, patient programmer 38 may be a handheldcomputing device. Patient programmer 38 may also include a display andinput keys to allow patient 10 to interact with patient programmer 38and neurostimulator 22. In this manner, patient programmer 38 providespatient 10 with an interface for control of neurostimulation therapy byneurostimulator 22. For example, patient 10 may use patient programmer38 to start, stop or adjust neurostimulation therapy. In particular,patient programmer 38 may permit patient 10 to adjust stimulationparameters such as duration, amplitude, pulse width and pulse rate,within an adjustment range specified by the clinician via clinicianprogrammer 38, or select from a library of stored stimulation therapyprograms.

Neurostimulator 22, clinician programmer 36, and patient programmer 38may communicate via cables or a wireless communication, as shown inFIG. 1. Clinician programmer 36 and patient programmer 38 may, forexample, communicate via wireless communication with neurostimulator 22using RF telemetry techniques known in the art. Clinician programmer 36and patient programmer 38 also may communicate with each other using anyof a variety of local wireless communication techniques, such as RFcommunication according to the 802.11 or Bluetooth specification sets,infrared communication, e.g., according to the IrDA standard, or otherstandard or proprietary telemetry protocols.

In the application of therapy system 20 shown in FIG. 1, implantation oflead 24 may involve the subcutaneous placement of lead 24 transverselyacross one or more occipital nerves 12, 14, and/or 16, or a branch ofthe same, that are causing patient 10 to experience pain.

FIG. 2 illustrates lead 24 and introducer needle 32, which is positionedproximate to target stimulation site 28 of patient 10. Lead 24 isaligned to be introduced into introducer needle 32. In particular, lead24 is aligned to be implanted and anchored or fixated with activelydeployable clip 30 proximate to target stimulation site 28 withinpatient 10 for stimulation of one or more occipital nerve 12, 14 or 16.In FIG. 2, clip 30 is in an undeployed state and has a substantiallystraight shape. In order to locate the specific nerve causing pain, aclinician may palpate the area of pain. In addition, some embodiments, ascreening lead may be used prior to implanting lead 24 to developoptimal stimulation parameters (e.g., various electrode combinations,amplitude, pulse width or rate).

In one example method of implanting lead 24 proximate to one or moreoccipital nerves 12, 14, 16, a vertical skin incision 34 approximatelytwo centimeters in length is made in the neck of patient 10 lateral tothe midline of the spine at the level of the C1 vertebra. Fluoroscopymay be used to identify the location of the C1 vertebra. Typically,local anesthetic is used during the implantation procedure. The lengthof vertical skin incision 34 may vary depending on the particularpatient. At this location, the patient's skin and muscle are separatedby a band of connective tissue referred to as fascia. In anothertechnique, an incision is made in trapezius muscle 25 of patient 10.

Introducer needle 32, which may be a Tuohy needle, is introduced throughincision 34 into the subcutaneous tissue, superficial to the fascia andmuscle layer but below the skin. In some embodiments, introducer needle32 may be manually curved by the clinician to conform to the contour ofthe body of patient 10 proximate to target stimulation site 28, and inthe embodiment shown in FIG. 2, the clinician may conform introducerneedle 32 to the contour of the neck of patient 10. In otherembodiments, introducer needle 32 may have a preformed curve.

Occipital nerves 12, 14, and 16 are located within the cervicalmusculature and overlying fascia, and as a result, introducer needle 32,and eventually lead 24, are inserted superior to occipital nerves 12,14, and 16. That is, in one embodiment, introducer needle 32 isintroduced into the fascia layer of patient 10 such that introducerneedle 32 is between the skin of patient 10 and target stimulation site28.

Introducer needle 32 may be guided transversely from incision 34 acrossthe midline of the spine of patient 10 to target stimulation site 28. Astylet may be disposed within introducer needle 32 to provide aclinician with a device to manipulate introducer needle 32 with control.Fluoroscopic observation may aid the clinician in identifying the trunkof the occipital nerve. Once introducer needle 32 is fully inserted, aneedle stylet may be removed from the introducer needle, if introducerneedle 32 includes a stylet. Lead 24 may then be advanced throughintroducer needle 32 and positioned to allow stimulation of targetstimulation site 28. A stylet may also be disposed within lead 24 tohelp guide lead 24 to target stimulation site 28. The position of lead28 may be verified via fluoroscopy or another suitable technique. Inaddition, the clinician may confirm that electrodes 26 proximate todistal end 24B of lead 24 are properly placed with respect to targetstimulation site 28. For example, the clinician may provide electricalsignals to electrodes 26 and patient 10 may provide feedback relating tothe paresthesia coverage.

Upon placement of lead 24, introducer needle 32 may be removed (eitherbefore or after confirming the placement of the electrodes 26). Clip 30may be deployed either before or after withdrawing introducer needle 32from patient 10. Upon deployment, clip 30 changes shape and engages withsurrounding tissue to substantially fix a position of lead 24 proximateto target stimulation site 28. For example, clip 30 of lead 24 may bedeployed into tissue adjacent to an occipital nerve 12, 14 or 16).Alternatively, clip 30 of lead 24 may extend around the outer perimeterof an occipital nerve 12, 14 or 16.

Accurate lead placement may affect the success of occipital nervestimulation, as well as any other tissue stimulation application oftherapy system 20. If lead 24 is located too deep, i.e. anterior, in thesubcutaneous tissue, patient 10 may experience muscle contractions,grabbing sensations, or burning. Such problems may additionally occur iflead 24 migrates after implantation. Furthermore, due to the location ofimplanted lead 24 on the back of the neck of patient 10, lead 24 may besubjected to pulling and stretching that may increase the chances oflead migration. For these reasons, fixating lead 24 with clip 30 may beadvantageous.

FIG. 3 is a block diagram illustrating various components ofneurostimulator 22 and an implantable medical lead 24. Neurostimulator22 includes therapy delivery module 40, processor 42, memory 44,telemetry module 46, and power source 47. In some embodiments,neurostimulator 22 may also include a sensing circuit (not shown in FIG.3). Implantable medical lead 24 includes lead body 48 extending betweenproximal end 48A and distal end 48B. Proximal end 48A of lead body 48,includes contacts (not shown in FIG. 3) to electrically couple lead 24(and in particular, electrodes 26) to a lead extension orneurostimulator 22 (FIG. 1). In the embodiment of FIG. 3 lead body 48 iscylindrical. In other embodiments, lead body 48 may be paddle-shaped(i.e., a “paddle” lead), in which case lead body 48 would define twoopposing surfaces, as shown in FIGS. 11 and 12 with respect to leads 86and 96, respectively.

Electrodes 26A, 26B, 26C, and 26D (collectively “electrodes 26”) aredisposed on lead body 48 adjacent to distal end 48B of lead body 48. Insome embodiments, electrodes 26 may be ring electrodes. In otherembodiments, electrodes 26 may be segmented or partial ring electrodes,each of which extends along an arc less than 360 degrees (e.g., 90-120degrees) around the circumference of lead body 48. The configuration,type, and number of electrodes 26 illustrated in FIG. 3 are merelyexemplary.

In embodiments in which lead 24 is a paddle lead, electrodes 26 mayextend along one side of lead body 48. Electrodes 26 extending around aportion of the circumference of lead body 48 or along one side of apaddle lead may be useful for providing an electrical stimulation fieldin a particular direction/targeting a particular therapy delivery site.For example, in the electrical stimulation application shown in FIG. 1,electrodes 26 may be disposed along lead body 48 such that theelectrodes face toward target stimulation site 28 or otherwise away froma scalp of patient 10. This may be an efficient use of stimulationbecause electrical stimulation of the scalp may not provide any or veryminimal useful therapy to patient 10. In addition, the use of segmentedor partial ring electrodes 26 may also reduce the overall powerdelivered to electrodes 26 by neurostimulator 22 because of theefficient delivery of stimulation to target stimulation site 28 byeliminating or minimizing the delivery of stimulation to unwanted orunnecessary regions within patient 10.

In embodiments in which electrodes 26 extend around a portion of thecircumference of lead body 48 or along one side of a paddle lead, leadbody 48 may include one or more orientation markers 50 proximate toproximal end 48A that indicate the relative location of electrodes 26.Orientation marker 50 may be a printed marking on lead body 48, anindentation in lead body 48, a radiographic marker, or another type ofmarker that is visible or otherwise detectable (e.g., detectable by aradiographic device) by a clinician. Orientation marker 50 may help aclinician properly orient lead 24 such that electrodes 26 face thedesired direction (e.g., toward target stimulation 28) within patient10. For example, orientation marker 50 may also extend around the sameportion of the circumference of lead body 48 or along the side of thepaddle lead as electrodes 26. In this way, orientation marker 50 facesthe same direction as electrodes 26, thus indicating the orientation ofelectrodes 26 to the clinician. In one embodiment, when the clinicianimplants lead 24 in patient 10, orientation marker 50 may remain visibleto the clinician.

Neurostimulator 22 delivers stimulation therapy via electrodes 26 oflead 24. In particular, electrodes 26 are electrically coupled to atherapy delivery module 40 of neurostimulator 22 via conductors withinlead body 48. In one embodiment, an implantable signal generator orother stimulation circuitry within therapy delivery module 40 deliverselectrical signals (e.g., pulses or substantially continuous-timesignals, such as sinusoidal signals) to targets stimulation site 28(FIG. 1) via at least some of electrodes 26 under the control of aprocessor 42. The implantable signal generator may be coupled to powersource 47. Power source 47 may take the form of a small, rechargeable ornon-rechargeable battery, or an inductive power interface thattranscutaneously receives inductively coupled energy. In the case of arechargeable battery, power source 47 similarly may include an inductivepower interface for transcutaneous transfer of recharge power.

The stimulation energy generated by therapy delivery module 40 may beformulated as neurostimulation energy, e.g., for treatment of any of avariety of neurological disorders, or disorders influenced by patientneurological response. The signals may be delivered from therapydelivery module 40 to electrodes 26 via a switch matrix and conductorscarried by lead 24 and electrically coupled to respective electrodes 26.

Processor 42 may include a microprocessor, a controller, a DSP, an ASIC,an FPGA, discrete logic circuitry, or the like. Processor 42 controlsthe implantable signal generator within therapy delivery module 40 todeliver neurostimulation therapy according to selected stimulationparameters. Specifically, processor 42 controls therapy delivery module40 to deliver electrical signal s with selected amplitudes, pulse widths(if applicable), and rates specified by the programs. In addition,processor 42 may also control therapy delivery module 40 to deliver theneurostimulation signals via selected subsets of electrodes 26 withselected polarities. For example, electrodes 26 may be combined invarious bipolar or multi-polar combinations to deliver stimulationenergy to selected sites.

Processor 42 may also control therapy delivery module 40 to deliver eachstimulation signal according to a different program, therebyinterleaving programs to simultaneously treat different symptoms orprovide a combined therapeutic effect. For example, in addition totreatment of one symptom such as a migraine headache, neurostimulator 22may be configured to deliver neurostimulation therapy to treat othersymptoms such as back pain.

Memory 44 of neurostimulator 22 may include any volatile or non-volatilemedia, such as a RAM, ROM, NVRAM, EEPROM, flash memory, and the like. Insome embodiments, memory 44 of neurostimulator 22 may store multiplesets of stimulation parameters that are available to be selected bypatient 10 via patient programmer 38 (FIG. 1) or a clinician viaclinician programmer 36 (FIG. 1) for delivery of neurostimulationtherapy. For example, memory 44 may store stimulation parameterstransmitted by clinician programmer 36 (FIG. 1). Memory 44 also storesprogram instructions that, when executed by processor 42, causeneurostimulator 22 to deliver neurostimulation therapy. Accordingly,computer-readable media storing instructions may be provided to causeprocessor 42 to provide functionality as described herein.

In particular, processor 42 controls telemetry module 46 to exchangeinformation with an external programmer, such as clinician programmer 36and/or patient programmer 38 (FIG. 1), by wireless telemetry. Inaddition, in some embodiments, telemetry module 46 supports wirelesscommunication with one or more wireless sensors that sense physiologicalsignals and transmit the signals to neurostimulator 22.

As previously discussed, migration of lead 24 following implantationwithin patient 10 may be undesirable, and may have detrimental effectson the quality of therapy delivered to patient 10. For example, withrespect to the occipital nerve stimulation application shown in FIG. 1,migration of lead 24 may cause displacement of electrodes 26 withrespect to target stimulation site 28. In such a situation, electrodes26 may not be properly positioned to deliver therapy to targetstimulation site 28, resulting in reduced electrical coupling, andpossibly undermining therapeutic efficacy of the neurostimulationtherapy from therapy system 20.

Substantially fixing lead 24 to tissue proximate to target stimulationsite 28 near occipital nerves 12, 14, 16 may help prevent lead 24 frommigrating from target stimulation site 28 following implantation, whichmay ultimately help avoid harmful effects that may result from amigrating lead 24. To that end, lead 24 includes actively deployableclip 30.

Actively deployable clip 30 provides a minimally invasive fixationmechanism for substantially fixing lead 24 proximate to targetstimulation site 28. As described above with respect to FIG. 2, targetstimulation site 28, which may be proximate to occipital nerves 12, 14,16 or branches thereof, are typically located relatively close to ascalp of patient 10. Accordingly, it may be desirable to provide lead 24with a fixation element that does not substantially protrude from leadbody 48 of lead 24 in order to help minimize interference between thefixation element and the scalp of patient 10. Alternatively, it may bedesirable to provide lead 24 with fixation element(s) that extend awayfrom a side of lead body 48 that does not engage with the scalp,epidermis or other integumentary layer of patient 10 when lead 24 isimplanted within patient 10. An example of such a fixation elementarrangement is described in U.S. patent application Ser. No. ______(attorney docket no. 1023-603US01/P-27173.00) by Martin T. Gerber,entitled, “IMPLANTABLE MEDICAL ELONGATED MEMBER INCLUDING FIXATIONELEMENTS ALONG AN INTERIOR SURFACE,” which was filed on Oct. 31, 2006.Minimal interference between clip 30 and the scalp of patient 10 maycontribute to the comfort of patient 10 and avoidance of tissue erosionor damage attributable to engagement between clip 30 and the scalp,epidermis or other integumentary layer of patient 10 when lead 24 isimplanted in patient 10.

In one embodiment, the deployed clip 30 located at a distal end 48B oflead body 48 is sized such that clip 30 does not protrude past alongitudinal outer surface 48C of lead body 48, which extends betweenproximal end 48A and distal end 48B, thereby reducing interferencebetween clip 30 and the scalp of patient 10. Even in embodiments inwhich an actively deployable clip 30 extends from longitudinal outersurface 48C (e.g., as shown in FIGS. 9 and 10), clip 30 may be shapedand sized to minimize interference with the scalp of patient 10. Forexample, clip 30 may be shaped to have a relatively blunt surface thatinteracts with the scalp, or clip 30 may be sized such that clip 30 doesnot engage with the scalp.

In some embodiments, clip 30 may also have a sharp tip 30A that isconfigured to penetrate into tissue near the target tissue site 28. Forexample, in embodiments in which lead 24 and clip 30 are implantedproximate to an occipital or trigeminal nerve, tip 30A of clip 30 may beshaped to penetrate through fascia. In embodiments in which tissueingrowth around clip 30 is desirable, such as when lead 24 is implantedin a region that undergoes a relatively large range of motion orfrequent motion, clip 30 may also have a rough outer surface to promotetissue ingrowth. Tissue ingrowth may help further stabilize lead 24.However, in some embodiments, such as when removability of lead 24 ishighly desired, tissue ingrowth may be undesirable, in which case clip30 may be formed to have a relatively smooth outer surface to inhibittissue adherence.

FIG. 4A is a schematic perspective view of lead 24, where clip 30 (shownin phantom lines) is in an undeployed state (i.e., a first state), andFIG. 4B is a schematic perspective view of lead 24 with clip 30 in adeployed state (i.e., a second state). Clip 30 includes a first bodyportion 30A (shown in phantom lines) that extends along the length oflead body 48 and a second portion 30B. First and second body portions30A and 30B are substantially cylindrical. However, in otherembodiments, first body portion 30A and/or second body portion 30B mayhave any suitable shape. For example, first body portion 30A may be aflat ribbon, which may increase a surface for contacting and engagingwith surrounding tissue.

Actively deployable clip 30 may be composed at least in part of anelastically deformable material wire that changes shape, e.g., from asubstantially straight or slightly curved shape as shown in FIG. 4A to amoderately or highly curved shape as shown in FIG. 4B. In the embodimentshown in FIG. 4B, second portion 30B of clip 30 has a substantiallyspiral shape in the deployed state.

In FIG. 4A, clip 30 is retained within retainer mechanism 52, which maybe any suitable apparatus that is capable of retaining clip 30, and inparticular, second portion 30B of clip 30, in an undeployed state. Forexample, retainer mechanism 52 may be a sheath, a wrap, introducerneedle (e.g., a Tuohy needle) or binder disposed around clip 30 and/orlongitudinal outer surface 48C of lead body 48.

Retainer mechanism 52 is disposed within a lumen 53 defined by lead body48 and substantially surrounds body portion 30A of clip 30. Lumen 53extends through the length of lead body 48 such that distal end 48B oflead body 48 defines an opening 53A. Retainer mechanism 52 may extendthrough lumen 53 and opening 53A to surround second portion 30B of clip30 to help maintain second portion 30B in a substantially undeployedstate. In this way, retainer mechanism 52 helps prevent prematureactivation of clip 30 (e.g., prior to lead 24 reaching targetstimulation site 28). In some embodiments, retainer mechanism 52 abutsthe outer surface of clip 30, while in other embodiments, there is aclearance between retainer mechanism 52 and clip 30 when retainermechanism 52 is disposed within lumen 53 of lead body 48. Lead body 48may also include stylet lumen 51 that extends substantially parallel tolumen 53 and is configured to receive a stylet. During implantation oflead 24 within patient 24, a clinician may manipulate a stylet disposedwithin stylet lumen 51 to manipulate and bend the distal tip 48B of leadbody 48 to guide lead 24 through patient 10 and reach target stimulationsite tissue 28.

In an alternate embodiment, clip 30 may not include body portion 30Aextending through lead body 48. For example, clip 30 may be attacheddirectly or indirectly to distal end 48B of lead body 48, such as withan adhesive, welding (e.g., ultrasonic welding) or clip 30 may beintegrally molded with lead body 48. In another embodiment, body portion30A of clip 30 may extend only part way through the length of lead body48 (measured between proximal end 48A and distal end 48B).

When a clinician desires to deploy clip 30, the clinician may axiallyretract retainer mechanism 52 from lead body 48. Once retainer mechanism52 is withdrawn past opening 53A in lead body 48 and second portion 30Bof clip 30 is released from retainer mechanism 52, second portion 30B ofclip 30 assumes a spiral shape in the example of FIG. 4B. The spiralshape increases the outermost dimension D (shown in FIG. 4B) of secondportion 30B of clip 30 and enables clip 30 to engage with surroundingtissue. Outermost dimension D is not necessarily the diameter of thesecond, deployed shape of clip 30 because the second shape of clip 30may not have a circular cross-section, but in some embodiments,outermost dimension D may be the diameter of the second shape of clip30. The curvilinear shape of second portion 30B of clip 30 also enableslead 24 to resist both movement in both axial and radial directions, andresist pulling forces from both proximal and distal directions. Leadbody 48 may be subjected to a pulling force from proximal end 48Abecause proximal end 48A is fixed to neurostimulator 22 (FIG. 1). Leadbody 48 may also be subject to other types of forces because lead 24 maybe implanted in a region of patient 10 (e.g., a neck of patient 10) thatundergoes a range of motion.

Other types of restraint mechanisms 52 may be used to restrain clip 30.For example, a wrap or binder that extends about clip 30 to hold it inits unexpanded position may be severed, cut, squeezed or crushed usingany of a variety of surgical tools to permit the clip 30 to deploy. Inaddition, clip 30 may be deployed via any suitable technique in additionto releasing clip 30 from restraint mechanism 52. For example, in oneembodiment, first body portion 30A of clip 30 may be disposed withinlumen 53, and first body portion 30A may be deployed therefrom bypushing first body portion 30A out of lumen 53 with a stylet disposedwithin lumen 53.

In some embodiments, the elastically deformable material wire used toform deployable clip 30 may be a shape memory polymer or metal, such asNitinol (a nickel titanium based alloy). A shape memory polymer or metalmay have superelastic and memory properties. The elastically deformablematerial may include additional elements in addition to Nitinol whichaffect the yield strength of the material or the temperature at whichparticular pseudoelastic or shape transformation characteristics occur.The transformation temperature may be defined as the temperature atwhich a shape memory material finishes transforming from martensite toaustenite. Upon heating the elastically deformable material may exhibitpseudoelastic (superelastic) behavior when deformed at a temperatureslightly above its transformation temperature. For example, if theelastically deformable material forming clip 30 is a shape memory alloy,a portion of the shape memory alloy may be converted from its austeniticphase to its martensitic phase when clip 30 is in its deployedconfiguration. As the stress is removed, the elastically deformablematerial may undergo a martensitic to austenitic conversion and springback to its original undeformed configuration (i.e., the deployed stateof clip 30). For example, a shape memory alloy metal may be formed intoan elastically deformable material by first wrapping a wire onto amandrel and heat treating the wire at approximately 400-500 degreesCelsius for approximately five to thirty minutes. The wire may be thenair quenched at room temperature. The mandrel may have a constantdiameter or may be conical in shape.

Other biocompatible materials such as stainless steel, titanium orbiocompatible polymeric materials may be used to form clip 30. In someembodiments, clip 30 may be formed at least in part of an electricallyconductive material, such as an electrically conductive shape memorymetal alloy. For example, at least a part of second portion 30B of clip30 may be electrically conductive. Lead 24 may include an electricalconductor that is configured to electrically connect clip 30 toneurostimulator 22 (or another medical device). Alternatively, bodyportion 30A of clip 30 may include an electrically conductive materialto enable body portion 30A to function as an electrical conductor toelectrically connect clip 30 to neurostimulator 22. In either case,proximal end 24A of lead 24 may include an electrical contact that iselectrically connected to the electrical conductor (whether it is aseparate electrical conductor or body portion 30A of clip 30) toelectrically couple electrically conductive clip 30 to neurostimulator22 or another medical device, such as a sensor.

In this way, actively deployable fixation clip 30 may serve dualfunctions. First, clip 30 may engage with surrounding tissue tosubstantially fix a position of lead 24. Second, clip 30 may act as anelectrode of lead 24 in addition to or instead of electrodes 26 todeliver stimulation therapy from neurostimulator 22 to targetstimulation site 28. As described below in reference to FIG. 5B, giventhe ability of clip 30 to retain a curvilinear shape in the deployedstate, clip 30 may be used as a cuff electrode in embodiments in whichclip 30 is at least partially electrically conductive. In someembodiments, clip 30 may be electrically coupled to at least one otherelectrode 26, and the electrically connected clip and electrode 26 mayact as a single electrode. In other embodiments, clip 30 may beindependent of electrodes 26 and may be a delivery electrode (i.e., usedto deliver stimulation to target tissue site 28). In yet otherembodiments, clip 30 may be independent of electrodes 26 and may, forexample, act as a return electrode for at least one of electrodes 26 ora sensing electrode that monitors a physiological parameter of thepatient.

FIG. 5A is a schematic diagram illustrating lead 24 implanted withinpatient 10 proximate to third occipital nerve 16. Clip 30 has beendeployed into tissue 54 adjacent to third occipital nerve 16 and engageswith surrounding tissue 54 to substantially fix electrodes 26 proximateto third occipital nerve 16 to provide electrical stimulation therapy tothird occipital nerve 16. Tissue ingrowth may be desirable in such anarrangement between clip 30 and nerve 16. In FIG. 5A (as well as theother figures), the relative positions and sizes of lead 24, electrodes26, clip 30, and third occipital nerve 16 are merely shown for purposesof illustration and are not intended to be drawn to scale. In general, acertain minimum distance between clip 30 and third occipital nerve 16 isdesired in order to help prevent inflammation to third occipital nerve16, and in some cases, unintended nerve damage. Clip 30 helps maintainthe minimum distance between electrodes 26 and third occipital nerve 16.In embodiments in which clip 30 is an electrode of lead 24, clip 30 mayalso be positioned the minimum distance from third occipital nerve 16.

In FIGS. 5A and 5B, third occipital nerve 16 is shown merely to aid inthe description of clip 30, and in other embodiments, lead 24 and clip30 may be implanted proximate to one or more of the other occipitalnerve 12, 14, a branch nerve of occipital nerves 12, 14, 16 or any othernerve, organ, muscle, muscle group or tissue site within patient 10.

FIG. 5B is a schematic diagram illustrating lead and clip 30, which hasbeen deployed around third occipital nerve 16. During implantation, clip30 may be guided and positioned such that when clip 30 is deployed, clip30 wraps at least partially around third occipital nerve 16. Contactbetween clip 30 and third occipital nerve 16 is generally undesirable.Thus, in an embodiment in which clip 30 is deployed around thirdoccipital nerve 16 (or another nerve), the second, deployed state ofclip 30 is sized and shaped to wrap around nerve 16 without engagingwith third occipital nerve 16. Tissue ingrowth around clip 30 may beundesirable in some embodiments in which clip 30 is deployed around anerve. In some patients, occipital nerves 12, 14, 16 may each have adiameter of about 1 millimeters (mm) to about 3 mm. Thus, at least withrespect to those patients, clip 30 may be sized and shaped such that ina deployed state (FIG. 4B), outermost dimension D of clip 30 is about 4mm to about 6 mm. However, outermost dimension D of clip 30 in adeployed state may differ depending upon the particular anatomy ofpatient 10 and the particular size of the nerve to be stimulated.

Deploying clip 30 around third occipital nerve 16 may be useful inembodiments in which clip 30 acts as an electrode for lead 24. Bywrapping around at least a part of the outer surface of third occipitalnerve 16, clip 30 may be a cuff electrode that provides electricalstimulation therapy to a relatively large surface area of thirdoccipital nerve 16. In addition, the close proximity of an electricallyconductive clip 30 to third occipital nerve 16 may also help reduce thepower required to deliver the stimulation therapy to third occipitalnerve 16. Actively deployable clip 30 provides a clinician with aminimally invasive technique for implanting a cuff electrode around anerve, such as occipital nerve 12, 14 or 16.

Although a sheath is shown as a retainer mechanism in FIGS. 4A-4B, anysuitable retainer mechanism may be used to restrain an activelydeployable clip in an undeployed state. FIGS. 6A-C illustrate schematicperspective views of lead 55, which includes another embodiment of aretainer mechanism, and in particular, clip retainer 56. Clip retainer56 includes a frangible seam 57 and seam breaker 58 that is at leastpartially embedded within frangible seam 57. Second portion 30B of clip30 (shown in FIGS. 5B and 5C) is disposed within a cavity 56A (shown inFIGS. 5B and 5C) defined by clip retainer 56. As previously discussed,in some embodiments, clip 30 may be attached to distal end 48B of leadbody 48, in which case clip 30 may not include body portion 30A (shownin FIG. 4A), and may only include second portion 30B. Alternatively,clip 30 may be attached to clip retainer 56, which, in the embodimentshown in FIGS. 6A-c, is attached to distal end 48B of lead body 48. Inother embodiments, clip retainer 56 may be attached to other portions oflead body 48, such as longitudinal outer surface 48C.

Frangible seam 57 covers cavity 56A of clip retainer 56 in order to helpcontain second portion 30B of clip 30 within cavity 56A. Frangible seam57 may be formed of a material that is capable of retaining clip 30 inan undeployed state, but also capable of break upon the application of aforce applied by seam breaker 58. For example, frangible seam 57 may beformed of a relatively thin wall polymer, paper, plastic, thin metal,biosorbable materials, or combinations thereof. Similarly, seam breaker58 is formed of a flexible material that has sufficient strength tobreak through frangible seam 57. For example, seam breaker 58 may beformed of a polymer, a metal or combinations thereof.

Once lead 55 is positioned proximate to target stimulation site 28, theclinician may actively deploy clip 30 by pulling on proximal end 58A ofseam breaker 58. Seam breaker 58 is embedded within frangible seam 57,and is oriented such that when proximal end 58A of seam breaker 58 ispulled in a proximal direction (indicated by arrow 59), distal portion58B of seam breaker 58 also moves in a proximal direction. As distalportion 58B of seam breaker 58 moves in a proximal direction, distalportion 58B breaks through frangible seam 57. FIG. 6C illustrates howseam breaker 58 opens frangible seam 57 and exposes cavity 56A of clipretainer 56. As shown in FIGS. 6B and 6C, upon the breaking of frangibleseam 57, cavity 56A is exposed and clip 30 is released therefrom,thereby enabling body portion 30B of clip to change shape and achieve adeployed state.

FIGS. 1-6C illustrate lead 24 that includes a single clip 30 includingsecond portion 30B that engages with tissue, where the second portion30B is disposed near distal end 48B of lead body 48 of lead 24. In otherembodiments, a lead may include any suitable number of activelydeployable clips disposed in any suitable arrangement with respect to alead body 48 of the lead. Examples of these other arrangements are shownin FIGS. 7-10.

FIG. 7 illustrates a schematic perspective view of lead 60, whichincludes actively deployable clips 64 and 66 disposed along longitudinalouter surface 48C of lead body 48. Clips 64 and 66 are shown in theirrespective deployed states in FIG. 7. Clips 64 and 66 may be used inaddition to or instead of clip 30 (shown in FIGS. 4A-6C) on a distal end48B of lead body 48. Clip 64 is located between electrodes 26 andproximal end 48A of lead body 48, and includes first body portion 64Aand second portion 64B. As shown in FIG. 7, when clip 64 is in adeployed state, second portion 64B of clip 64 has a curvilinear shape.Body portion 64A of clip 64 is attached to outer surface 48C of leadbody 48 using any suitable technique, such as by an adhesive, welding orbody portion 64A of clip 64 and lead body 48 may be integrally molded.In some embodiments, clip 64 may not include body portion 64A, andsecond portion 64B may be attached (directly or indirectly) to lead body48, as shown with respect to clip 66, which does not include a bodyportion that extends along longitudinal outer surface 48C of lead body48. Clip 66 is located between electrodes 26 and distal end 48B of leadbody 48. When clip 66 is in a deployed state, clip 66 also has acurvilinear shape.

As FIG. 7 illustrates, clips 64 and 66 extend from opposite sides oflead body 48. However, in other embodiments, clips 64 and 66 may extendfrom the same side of lead body 48 (i.e., share a radial position), oralternatively, clips 64 and 66 may have different radial positions withrespect to lead body 48.

Clips 64 and 66 need not have the same curvilinear shape or the samesize in the respective deployed states. For example, if lead 60 isimplanted proximate to occipital nerve 16 in patient 10 such that clip64 faces a deep direction (away from the scalp of patient 10) and clip66 faces a superficial direction (towards the scalp of patient 10), itmay be desirable for clip 66 to have a smaller outermost dimension inthe second, deployed state in order to minimize interference betweenclip 66 and the scalp of patient 10. As previously discussed, this mayhelp minimize irritation to patient 10 from clip 66 and may help avoiddamage to the scalp of patient from clip 66 extending into and possiblythrough the scalp.

A single restraint mechanism may be used to retain clips 64 and 66 in anundeployed state. For example, in the embodiment shown in FIG. 7, asingle introducer needle or single sheath 68 (shown partially withdrawnwith respect to distal end 48B of lead body 48) may be disposed aroundlead 60 and clips 64 and 66 during implantation of lead 60 in patient 10in order to restrain clips 64 and 66 in the respective undeployed stateand prevent premature engagement of clips 64 and 66 with surroundingtissue. In order to deploy clips 64 and 66 into surrounding tissue inorder to substantially fix a position of lead 60 with respect to targetstimulation site 28 (FIG. 1), sheath 68 may be withdrawn in a proximaldirection (as indicated by arrow 69). Axial retraction of sheath 68 maydeploy clips 64 and 66 in succession, one at a time, if clips 64 and 66are at different axial positions along a length of lead 60. Clip 66 istypically deployed before clip 64 if sheath 68 is withdrawn towardproximal end 48A of lead body 48.

Actively deployable clips 64 and 66 may each be formed of a deformablematerial. When sheath 68 is disposed around lead 60, actively deployableclips 64 and 66 may be compressed, thus minimizing the overall profileof lead 60. Minimizing the profile of lead 60 may help minimize theinvasiveness of an implantation procedure for lead 60 because a smallerdiameter lead introducer (e.g., introducer needle 32 shown in FIG. 2)may be used to accommodate the smaller profile lead body 60.

FIG. 8 illustrates lead 60 implanted proximate to third occipital nerve16 of patient 10. When lead 60 includes two or more clips forsubstantially fixing a position of lead 60 proximate to a targetstimulation site, the two or more clips may engage with two differenttissue regions, which may provide a more secure fixation of lead 60. Forexample, in the embodiment shown in FIG. 8, clips 64 and 66 are arrangedaround lead body 48 such that when deployed, clip 66 may be deployedinto tissue adjacent to third occipital nerve 16 and clip 64 may bedisposed around third occipital nerve 16. The two fixation pointsprovided by clip 64 and clip 66 proximal to and distal to electrodes 26may help locally fix electrodes 26 proximate to third occipital nerve16. In addition, in some embodiments, clip 64 and/or clip 66 may beelectrically conductive and may function as electrodes of lead 60.

While lead 60 of FIGS. 7 and 8 includes two actively deployable fixationclips 64 and 66, in other embodiments, a lead may include more than twoactively clips. Furthermore, in other embodiments, clips 64 and 66 maynot be arranged on opposite sides of lead body 48. For example, FIG. 9illustrates a schematic perspective view of lead 70, which includesclips 72 and 74 extending from the same side of lead body 48. Clips 72and 74 share a body portion 76, and clip 74 also includes a body portion74A that extends from shared body 76. In one technique for forming clips72 and 74 with a shared body portion 76, a piece of suitable materialfor forming clips 72 and 74 (e.g., a wire formed from a shape memorymaterial or an elastic material) may be cut to define clips 72 and 74.Body portions 74A and 76 may be coupled to lead body 48 using anysuitable means, such as an adhesive, welding or body portions 74A and 76and lead body 48 may be molded together.

An arrangement including clips 72 and 74 along one side of lead body 48of lead 70 may be useful when lead 70 is implanted within a subcutaneousregion of patient 10 because clips 72 and 74 may be oriented away fromthe epidermis, scalp or other integumentary layer of patient 10, therebyminimizing interference between clips 72 and 74 and the epidermis, scalpor other integumentary layer. An example of a lead with one or morefixation elements positioned along one side of lead body 48 is describedin further detail in U.S. patent application Ser. No. ______ (attorneydocket no. 1023-603US01/P-27173.00) by Martin T. Gerber, entitled,“IMPLANTABLE MEDICAL ELONGATED MEMBER INCLUDING FIXATION ELEMENTS ALONGAN INTERIOR SURFACE,” which was filed on Oct. 31, 2006.

In other embodiments, lead 70 may include clips extending from the sameside of lead body 48 that do not share a body portion or that do nothave a body portion that extends along the length of lead body 48. Forexample, clip 72 and/or clip 74 may have a configuration similar to clip66 of FIG. 7.

A lead may also include actively deployable clips between electrodes 26,as shown in FIG. 10. FIG. 10 illustrates a schematic perspective view oflead 80, which includes actively deployable clip 64 (also shown in FIG.7) and actively deployable clip 82. Clip 64 is disposed between proximalend 48A of lead body 48 and electrodes 26, while clip 82 is disposedbetween electrodes 26B and 26C. In another embodiment, lead 80 may alsoinclude an actively deployable clips located between distal end 48B oflead body 48 and electrodes 26 or at distal end 48B. Actively deployableclip 82 between electrodes 26B and 26C may help locally fix electrodes26 proximate to target stimulation site 28. Body portion 82A of activelydeployable clip 82 is disposed within lead body 48. In anotherembodiment, both clips 64 and 82 may be partially disposed within leadbody 48.

In each of leads 24, 55, 60, 70, and 80 of FIGS. 4A, 6A, 7, 9, and 10,respectively, lead body 48 is cylindrical. In another embodiment, a leadmay include a paddle-like shape portion (i.e. a paddle lead) and mayinclude one or more actively deployable clip fixation elements at adistal end of the paddle-shaped portion and/or along one or morelongitudinal surfaces of the paddle-shaped portion.

FIG. 11 is a plan view of paddle lead 86, which includes substantiallyflat, paddle-like shaped lead body 88 extending between proximal end 88Aand distal end 88B and including electrodes 90 and actively deployablefixation clip 92. Proximal end 88A of lead body 88 is coupled to distalend 94A of lead body connector 94. A proximal end (not shown in FIG.12A) of lead body connector 94 may be direct or indirectly (e.g., via alead extension) coupled to a neurostimulator (e.g., neurostimulator 22of FIG. 1) or another medical device. Lead body 88 defines a “paddle”like shape, including first surface 88C and second surface 88D, which ison an opposite side of lead body 88 from first surface 88C.

In the embodiment shown in FIG. 11, electrodes 90 are carried by firstsurface 88C of lead body 88. In another embodiment, paddle lead 86 mayalso include electrodes along second surface 88D of lead body 88. Eachof the electrodes 90 may be electrically coupled to neurostimulator 22,lead extension or other medical device via electrical conductorsdisposed within lead body 88 and lead body connector 94. A proximal end(not shown in FIG. 11) of lead body connector 94 may include electricalcontacts for electrically connecting the electrical conductors withinlead body connector 94 to neurostimulator 22.

Extending from distal end 88B of lead body 88 is actively deployablefixation clip 92, which is shown in its deployed state. Clip 92 may beattached directly or indirectly to distal end 88B of lead body 88, ormay have a body portion that extends through lead body 88. When lead 86is implanted within patient 10, clip 92 may engage with surroundingtissue to substantially fix electrodes 90 proximate to targetstimulation site 28. In some embodiments, clip 92 may be at leastpartially conductive and may be an electrode for lead 86.

FIG. 12 is a plan view of paddle lead 96, which is another embodiment ofpaddle lead 86 of FIG. 11. Lead 96 includes actively deployable fixationclips 98 and 100 disposed along first and second surfaces 88C and 88D,respectively, of lead body 88. Clips 98 and 100 may be used in additionto or instead of clip 92 on distal end of lead body 88B, as shown inFIG. 11. Furthermore, lead 96 may include only one clip 98 or 100, whichmay be useful when lead 96 is implanted within a subcutaneous region ofpatient 10 because fixing lead 96 along one surface 88C or 88D may helpminimize interference between clip 98 or 100 and the epidermis, scalp orother integumentary layer of patient 10.

FIG. 13 is a flow diagram of a process for implanting a lead 24 (FIGS.1-5B) including at least one actively deployable fixation clip proximateto one of occipital nerves 12, 14 or 16. While lead 24 is referenced inthe description of FIG. 13, it should be understood that the process mayalso be used to implant any of leads 55, 60, 70, 80, 86 or 96 of FIGS.6A, 7, 9-12, respectively, or any other lead or implantable medicaldevice including at least one actively deployable fixation clip.Furthermore, in other embodiments, the process illustrated in FIG. 13may also be used to implant an implantable medical device including afixation clip proximate to any suitable tissue site within patient 10.

Where treating occipital neuralgia, patient 10 may be placed in alateral position or in a prone position during implantation of lead 24.Introducer needle 32 (shown in FIG. 2), or another introducer, isintroduced into patient 20 (FIG. 1) near target stimulation site 28(104), and a distal end of introducer needle 32 is guided to targetstimulation site 28. Introducer needle 32 may be inserted into patient10 percutaneously or via an incision (e.g., incision 34 in FIG. 2). Asdescribed in reference to FIG. 2, introducer needle 32 may be introducedinto subcutaneous tissue, superficial to the fascia and muscle layer ofpatient 10, but below the skin (or scalp) of patient 10. The clinicianmay guide introducer needle 32 to a region superior to occipital nerves12, 14, 16 or another nerve or tissue site to be stimulated. Introducerneedle 32 may have a preformed curve to follow the contour of the bodyof patient 10 at the insertion site, or the clinician may manually curveintroducer needle 32.

After introducer needle 32 reaches the desire site within patient (i.e.,a location proximate to target stimulation site 28), a stylet may beremoved from introducer needle 32 if introducer needle 32 includes astylet. Lead 24 is then introduced into a lumen of introducer needle 32(106). In particular, distal end 24B of lead 24 is introduced into thelumen before proximal end 24A. In some embodiments, lead 24 may bepreloaded into introducer needle 32, which may eliminate the need tointroduce lead 24 into the lumen of introducer needle 32. While clip 30is in an undeployed state, lead 24 is advanced through the lumen untilelectrodes 26 adjacent to distal end 48B of lead body 48B of lead 24 arepositioned proximate to target stimulation site 28 (108). For example,distal end 24B of lead 24 may be advanced through the lumen ofintroducer needle 32 until at least distal end 24B protrudes past thelumen and into tissue 54 (FIG. 5A) of patient 10 and undeployed clip 30protrudes past the distal tip of the introducer. Alternatively,undeployed clip 30 may be introduced into surrounding tissue 54 by atleast partially withdrawing introducer needle 32, thereby exposing lead24. Partially withdrawing introducer needle 32 allows the clinician toreinsert introducer needle 32 if repositioning of lead 24 is desired,while still exposing electrodes 26.

The clinician may confirm that electrodes 26 are operative positionedwith respect to target stimulation site 28, such as by providingelectrical stimulation to electrodes 26 and receiving feedback frompatient 10. Patient 10 may, for example, indicate the level of therapyprovided by the electrical stimulation, the area of coverage, and soforth. Alternatively, the clinician may confirm that electrodes 26 areproperly positioned with the aid of fluoroscopic imaging.

As discussed above, the clinician may aim to deploy clip 30 around atleast a part of an outer perimeter of a target occipital nerve 12, 14,or 16 (or another nerve within patient 10), such as when clip 30 is alsoan electrically conductive electrode. In such an application of lead 24,the clinician may position clip 30 with respect to the target nerve toachieve such an arrangement of clip 30 (108). Fluoroscopy or anothertechnique may be used to help the clinician precisely and accuratelyplace clip 30 to wrap around at least a part of the nerve.

The clinician may then deploy clip 30 by withdrawing restraint mechanism52 (FIG. 4A) or otherwise permitting clip 30 to change shape into thedeployed state (110). Once deployed, actively deployable clip 30 changesfrom a substantially straight or slightly curved shape to assume thespiral configuration shown in FIG. 4B. In the deployed shape, clip 30engages with surrounding tissue to substantially fix a position of lead24 proximate to target stimulation site 28 and substantially fixelectrodes 26 within the tissue to ensure reliable electrical contactwith target stimulation site 28. If lead introducer 32 has not beenwithdrawn from patient 20, the clinician may withdraw the leadintroducer 32 after deployment of clip 30 (112).

After securing electrical stimulation lead 24 with actively deployableclip 30, the clinician may connect proximal end 24A of lead 24 toneurostimulator 22. If an implantable neurostimulator 22 is used, theclinician may tunnel proximal end 24A of lead 24 to the implant site forimplantable neurostimulator 22. Various modifications to the describedtechniques of implantation of electrical stimulation lead 24 may bemade.

The position, pattern and number of electrodes carried by the variousleads described in this disclosure may vary. For example, some leads maycarry a single electrode or multiple electrodes. The electrodes may bearranged in a linear array, a two-dimensional array, or athree-dimensional array. The electrodes may take the form of electroderings, pads, or probes. In addition, the leads may take the form ofconventional axial leads with ring electrodes or paddle leads with atwo-dimensional array of electrode pads.

Electrodes carried by a given lead may form bipolar or multipolarelectrode combinations with electrodes on the same lead or electrodes ona different lead or leads. In addition, such electrodes may formunipolar electrode combinations with one or more electrodes carried byan implantable stimulation generator, e.g., on the housing or “can” inan active can arrangement. In addition, in some embodiments, anelectrical stimulation generator may carry integrated electrodes,forming a so-called leadless stimulator or “microstimulator.” In each ofthese cases, a deployable clip as described herein may be utilized tofix a lead, stimulation generator housing, or other implantable medicaldevice relative to a desired target site for delivery of electricalstimulation, drugs or other therapies.

An implantable medical device may include other types of fixationelements in addition to an actively deployable clip. For example, inaddition to an actively deployable clip, a lead may also include otheractively or passively deployed fixation element that helps preventmigration of the lead when the lead is implanted in patient 10, such as,but not limited to, one or more tines, barbs, hooks, adhesives (e.g.,surgical adhesives), balloon-like fixation elements, collapsible orexpandable fixation structures, a vacuum-receiving cavity and pinningmember, and so forth. The other fixation elements may be composed of anysuitable biocompatible material, including, but not limited to,titanium, stainless steel, Nitinol (a nickel titanium based alloy),other shape memory materials, hydrogel or combinations thereof.

A lead including one or more actively deployable fixation clips may beuseful for various electrical stimulation systems. For example, the leadmay be used to deliver electrical stimulation therapy to patients totreat a variety of symptoms or conditions such as chronic pain, tremor,Parkinson's disease, multiple sclerosis, spinal cord injury, cerebralpalsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy,pelvic floor disorders, gastroparesis, muscle stimulation (e.g.,functional electrical stimulation (FES) of muscles) or obesity. Inaddition, an actively deployable clip described herein may also beuseful for fixing a catheter, such as a drug deliver catheter, proximateto a target drug delivery site or a microstimulator to a target tissuesite within a patient.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

1. A system comprising: an implantable medical device; and a fixationelement coupled to the implantable medical device, the fixation elementcomprising an electrically conductive portion configured to at least oneof deliver electrical stimulation to a target tissue site within apatient or sense a physiological parameter from the target tissue site,wherein the fixation element is actively deployable from a first shapeto a second shape to resist substantial movement of the implantablemedical device from the target tissue site.
 2. The system of claim 1,wherein the second shape has an outermost dimension of at least abouttwo millimeters.
 3. The system of claim 2, wherein the outermostdimension of the second shape is between about two millimeters and aboutfive millimeters.
 4. The system of claim 1, further comprising aretainer that retains the fixation element in the first shape, whereinthe retainer releases the fixation element for deployment to the secondshape in response to manipulation of the retainer.
 5. The system ofclaim 4, wherein the retainer is at least one of a sheath or a devicedefining a cavity configured to receive the fixation element, the devicecomprising a frangible seam covering the cavity and a seam breakermember at least partially embedded in the frangible seam.
 6. The systemof claim 1, wherein the first shape is a substantially straight shape.7. The system of claim 1, wherein the second shape is a substantiallycurvilinear shape.
 8. The system of claim 7, wherein the second shape isa spiral shape.
 9. The system of claim 1, wherein the implantablemedical device is a lead comprising at least a first stimulationelectrode, and wherein at least a portion of the electrically conductiveportion of the fixation element is a second stimulation electrode of thelead.
 10. The system of claim 9, wherein the second stimulationelectrode is a cuff electrode configured to wrap around at least one ofan occipital nerve or a trigeminal nerve of the patient.
 11. The systemof claim 9, further comprising an electrical stimulation generatorcoupled to the lead, the fixation element being configured to deliverelectrical stimulation from the electrical stimulation generator to thetissue site within the patient.
 12. The system of claim 9, wherein thefixation element comprises a first fixation element located between thedistal end of the lead and the first stimulation electrode, the systemfurther comprising a second fixation element located between a proximalend of the lead and the first stimulation electrode.
 13. The system ofclaim 9, wherein the lead further comprises a third stimulationelectrode adjacent to the first stimulation electrode, wherein thefixation element is located between the first and third stimulationelectrodes.
 14. The system of claim 1, wherein the fixation element isattached to a distal end of the implantable medical device.
 15. Thesystem of claim 1, wherein the fixation element comprises a wire formedfrom one of an elastic material or a shape memory material.
 16. Thesystem of claim 1, wherein the implantable medical device comprises theelectrical stimulation generator.
 17. A medical lead comprising: a leadbody; an electrical conductor disposed within the lead body; a fixationelement comprising an electrically conductive portion electricallycoupled to the electrical conductor, wherein the fixation element isactively deployable from a first shape to a second shape to resistsubstantial movement of the lead body from a target therapy deliverysite in a patient.
 18. The medical lead of claim 17, wherein thefixation element is a first electrode and the medical lead furthercomprises at least a second electrode carried by the lead body.
 19. Themedical lead of claim 18, wherein the fixation element comprises a firstfixation element located distal to the second electrode and the medicallead further comprises a second fixation element located proximal to thesecond electrode.
 20. The medical lead of claim 18, wherein at least oneof the first or second electrodes is a sensing electrode.
 21. Themedical lead of claim 17, wherein the second shape is a substantiallycurvilinear shape.
 22. The medical lead of claim 17, wherein the portionof the fixation element is a cuff electrode configured to wrap around aperipheral nerve of a patient.
 23. The medical lead of claim 22, whereinthe peripheral nerve at least one of an occipital nerve or a trigeminalnerve of the patient.
 24. A method comprising: implanting an implantablemedical device in a body of a patient; and actively deploying a fixationelement coupled to the implantable medical device, the fixation elementcomprising an electrically conductive portion configured to at least oneof deliver electrical stimulation to a target tissue site within thebody of the patient or sense a physiological parameter from the targettissue site, wherein the fixation element is actively deployable from afirst shape to a second shape to resist substantial movement of theimplantable medical device from the target tissue site.
 25. The methodof claim 24, further comprising releasing the fixation element from aretainer for deployment to the second shape.
 26. The method of claim 25,wherein releasing the fixation element from the retainer compriseswithdrawing a sheath from around the fixation element.
 27. The method ofclaim 25, wherein the retainer defines a cavity and the retainercomprises: a frangible seam covering the cavity; and a seam breakermember at least partially embedded in the frangible seam, the fixationelement being disposed within the cavity, wherein releasing the fixationelement from the retainer comprises pulling a seam breaker member tobreak the frangible seam.
 28. The method of claim 24, wherein theimplantable medical device comprises a lead comprising at least a firststimulation electrode, wherein the fixation element is a secondstimulation electrode of the lead.
 29. The method of claim 24, furthercomprising positioning the fixation element with respect to a nerve of apatient such that when the fixation element deploys to the second shape,the fixation element wraps around at least a portion of the nerve.